Author:
Jae-Hee Ahn, Yo-Sub Han
Publisher:
CIAA 2009
Presenter:
Li-Hsien, Hsu
Data:
5/9/2012
1
Introduction
2
Introduction
3
Introduction
The size of a regular expression from
state elimination depends on the
state removal sequence.
2 -> 4
4 -> 2
4
Heuristics for State Elimination
 The Decomposition Heuristic
 vertical decomposition
 horizontal decomposition
 The State Weight Heuristic
5
Vertical Decomposition
 Definition 1. We define a state q in an FA A to be a bridge state if it
satisfies the following conditions:
1. State q is neither a start nor a final state.
2. For each string w ∈ L(A), its path in A must pass through q at least once.
3. State q is not in any cycle except for the self-loop.
6
Vertical Decomposition
7
Horizontal Decomposition
 For horizontal chopping of a given FA A = (Q,Σ, δ, s, f), we have to
identify subautomata of A such that all subautomata are disjoint from
each other except s and f.
8
The State Weight Heuristic
9
The State Weight Heuristic
In = 1
Out = 2
(1*2)+(1*1+1*1)+5*(1*2) = 14
10
 C-I
Eliminate states in order.
 C-II
Using VC & HC, and eliminate
States in order.
 C-III
Using SWH only once.
 C-IV
Using VC & HC, and eliminate
States with SWH only once.
 C-V
Using SWH in every steps.
 C-VI
Using VC & HC, and eliminate
States with SWH in every steps.
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